Vehicle diagnostic tool—utilizing rated horsepower vs. calculated horsepower

ABSTRACT

An analysis tool which extracts all the available parameter identifications (i.e. PIDS) from a vehicle&#39;s power train control module for diagnostic decisions. This is done by checking these PIDS and other information (e.g., calculated PIDS, Break Points, charts and algorithms) in three states; key on engine off, key on engine cranking, key on engine running. In all three modes the tool is comparing the live data from PIDS and voltage to the other information (e.g, Break Points). If any of this data are outside the programmed values a flag is assigned to the failure or control problem. The relationship between a particular PID and its associated preprogrammed value(s) may be indicated by a light. The depth of the problem (if any) is conveyed by the color of the light. Also included are tests/charts for fuel trim, engine volumetric efficiency, simulated injector, power, catalyst efficiency, and engine coolant range.

CLAIM OF PRIORITY

This application is a divisional of and claims the priority ofapplication Ser. No. 11/811,634, filed 8 Jun. 2007, which claimed thepriority of provisional application Ser. No. 60/812,525, filed 8 Jun.2006.

FIELD OF THE INVENTION

This invention relates to automotive diagnostic tools, particularly ananalysis tool that will interface with the power train control moduleand alert the automotive technician to problems with the engine controlsystem and/or the associated engine and/or other power plant systems, topermit such technician to zero in on such problems.

BACKGROUND OF THE INVENTION

With increasing government demands on emission control systems and fuelmileage concerns, the power plant of a vehicle has become a high techengineering marvel. This, in turn, means that the automotive technicianis faced with increasing difficulties of diagnosing and repairingcomplicated systems. Repairs must be completed in a timely manner whichhas become a problem for many automotive repair shops.

The modern vehicle (1996 and later models) has a number ofmicroprocessors including one programmed to control the runningparameters of the power plant (i.e., the powertrain control module). Thedata from this microprocessor provides the skilled technician withinformation that is needed in order to make diagnostic decisions aboutthe power plant. However, as the power plant systems become morecomplicated, more data and a better understanding of such data is neededin order to make accurate diagnostic decisions, thus making it moredifficult for technicians to see a problem when it occurs. Even ifavailable data is saved, a technician may overlook important informationand can misdiagnose the system.

DEFINITIONS

Unless otherwise indicated (e.g., Volumetric efficiency tests whichwould work on diesel engines) Power Plant includes:

-   -   a gasoline engine (including engines which also run on alternate        fuels, such as ethanol, either alone or mixed with gasoline);    -   powertrain control module (sometimes referred to by the acronym        PCM or ECM (for engine control module));    -   engine control system (sensors, such as an O2 sensor, that feed        data to the PCM and activators that carry out PCM commands, such        as fuel injectors, exhaust gas recirculator, and purge control);    -   starting system, including starter motor and “key”;    -   charging system;    -   air induction system (e.g., air filter, MAS (mass airflow        sensor; sometimes referred to by the acronym MAF);    -   fuel delivery system (e.g., fuel pump, fuel filter, fuel        pressure regulator, fuel pressure sensor, fuel damper,        injectors);    -   cooling system (e.g., radiator, water pump, thermostat); and    -   exhaust system.

The foregoing are intended to be illustrative. As those skilled in theart will appreciate the above are not necessarily mutually exclusive orexhaustive categories. For instance, the air induction system includesthe intake manifold which is generally considered part of the engine.Similarly, the fluid passages on the engine are part of the coolingsystem. Further, engines, depending on size, year of manufacture andmanufacturer, have different control systems (e.g., different numbersand locations of O2 sensors). While all fuel delivery systems include apump, fuel filter and injectors, not all include a fuel pressure sensoror a fuel damper. The term key, as used herein, includes any type ofstarting device, whether a traditional key and tumbler system, or alaser based or a frequency based device. Finally, unless otherwiseindicated, the term vehicle is intended to cover gasoline engine poweredvehicles, such as automobiles and light trucks. Other definitions (e.g.,PID/PIDS; Paragraph [0011]) are set forth elsewhere in thespecification.

OBJECTS OF THE INVENTION

What was needed is a way in which the automotive technician can easilyconnect to the automobile's power train control module with a devicethat could help diagnose the power plant systems quickly and accurately.

It is an object of the present invention to provide an analysis toolthat will interface with the power train control module and alert thetechnician to problems with, for instance, the engine control system asthey occur, to permit the technician to zero in on such problems as theyoccur.

It is a further object of the present invention to provide an analysistool with alert lights, whereby failures are brought to the attention ofthe technician as they occur.

Furthermore, it is an object of the present invention to provide anautomated analysis tool to help a technician that does not have thetechnical skill level needed to make correct diagnostic decisions.

SUMMARY OF THE INVENTION

The analysis tool of the present invention interfaces with the vehicle'sdata link connector (DLC) and communicates with the vehicle's powertrain control module (PCM). The tool extracts all the availableparameter identifications (i.e. PIDS). These PIDS, which containinformation from the inputs and outputs of the powertrain controlmodule, are utilized to make diagnostic decisions to help thetechnician. This can be done by checking these PIDS and otherinformation (e.g., calculated PIDS, Break Points, charts) in threestates; key on engine off (KOEO), key on engine cranking (KOEC), key onengine running (KOER). While this is the preferred order, other orderswould provide the same result.

The PIDS transmitted from the power train control module are monitored.In one aspect of the invention some monitored PIDS are compared to oneor more preprogrammed values. The relationship between a particular PIDand its associated preprogrammed value(s) (also referred to as BreakPoint(s)) (whether within range, less that or greater than theassociated Break Point) will be indicated to the technician by turningon an alert light. The depth of the problem (if any) is conveyed to thetechnician by the color of the alert light. A green alert lightindicates no current problems. A yellow alert light indicates that oneor more of the parameters have been crossed but that the problem issmall (e.g., no drivability problem; there is a high probability thatthe power plant functions according to the manufacturer'sspecifications). An orange alert light indicates that system has afailure (e.g., it is more probable that not that the power plant is notfunctioning according to the manufacturers' specifications; it is moreprobable than not that there is a drivability problem). A red alertlight indicates that the system failure needs immediate attention (e.g.,there is a high probability that there is a drivability problem). Therich (yellow) and lean (blue) indication alert lights are exceptions tothe foregoing. The alert lights are activated as the technician isviewing data displayed both digitally and in graph formats depending onthe information format selected.

In the KOEO (the first state in the automatic mode discussed below) theonboard microprocessor (PCM) has power but the engine is not inrotation. In this condition the open circuit battery voltage (calculatedPID or CPID) is checked, barometric pressure (PID) is check, throttleposition sensor (PID) is checked, engine coolant temperature (PID) ischecked, intake air temperature (PID) is checked, O2 bias voltage (PID)is checked (if applicable), diagnostic trouble codes (DTC's) arechecked, pending codes are checked and Mode 6 data is checked andanalyzed. A pending code is a DTC indicating that a component or systemhas failed one or more times, but (in accordance with a specificationprogrammed into the PCM by the vehicle manufacturer) has not failedenough times to be a matured DTC. Some DTCs are displayed on thevehicle's dash board as an amber light or icon.

In the KOEC (the second state in the automatic mode) the onboardmicroprocessor has power and the starter is engaged loading theelectrical system. As the engine is rotated the piston movement createsa light pressure differential in the intake manifold. In this conditionthe battery voltage (CPID) is checked, cranking vacuum (CPID) ischecked, cranking RPM (PID) is checked.

In the KOER (the third state in the automatic mode) the microprocessorhas power and the engine is running. The microprocessor (PCM) iscontrolling the running parameters of the power plant. In this conditionthe battery charging voltage (taken off the DLC or data link connector)is checked, engine running vacuum is checked, volumetric efficiency ofthe engine is checked (CPID), catalyst efficiency (CPID) is checked,fuel control (CPID) is checked, fuel trim (a correction factor set bythe vehicle manufacturer) (PID) is checked, time to engine temperature(CPID) is checked, engine coolant sensor (PID) and cooling system (anAlgorithm) are checked, intake air temperature (PID) is checked, massair flow sensor (PID) is checked if present on vehicle, oxygen sensors(PIDS) are checked, throttle position sensor (PID) is checked, ignitiontiming advance is checked (PID), pending codes (PID) are checked, andMode 6 data (i.e., PCM or powertrain control module testing sequence) ischecked and analyzed.

In all three modes of operation (whether manual or the automatedversion) the analysis tool is comparing the live data from the PIDS andvoltage from the DLC to parameters (e.g, Break Points, calculated PIDS,charts and algorithms) that have been programmed into the system. If anyof this data are outside the programmed parameters a flag is assigned tothe failure or control problem.

In the alternative, a technician can choose to run the foregoing testsin an automated sequence. In this scenario the technician will be askedseveral basic questions (e.g., make and model of the vehicle). (See FIG.39.) Once these questions are answered the system will proceed with atesting sequence, in the order identified above, that will identifyfailing parameters and chart this information. In the automated mode,once the testing sequence is completed and all data has been collectedthe analysis tool evaluates this flagged data and rationality data(e.g., the EGR (exhaust gas recirculation) being stuck on) and projectsa probable solution so that the technician can then correct the powerplant failure(s).

BRIEF DESCRIPTION OF THE DRAWINGS

The application file contains at least one drawing executed in color.Copies of this patent or patent application publication with colordrawing(s) will be provided by the Office upon request and payment ofthe necessary fee.

FIG. 1 is a schematic illustrating the inputs and outputs to theanalysis tool of the present invention;

FIG. 2 is a sample color screen display of the analysis tool of thepresent invention showing slide bars with a digital display and certainalert lights activated;

FIG. 3 is a sample color screen display showing the incoming data ingraph form, with a digital readout, and certain alert lights activated;

FIG. 4 is a color screen display of the tool of the present inventionshowing the DTC codes pulled for a 2000 Toyota 4Runner;

FIG. 5 is a color screen display showing the Mode 6 data for the 2000Toyota 4Runner;

FIG. 6 is a color screen display showing the Mode 5 (the tab is marked“O2” as technicians generally understand O2 sensor testing but may notbe familiar with the designation “Mode 5”) data for the Toyota 4Runner;

FIG. 7 is a color screen display showing the monitors for the Toyota4Runner;

FIG. 8 is a color screen display showing the PIDS for the 2000 Toyota4Runner;

FIG. 9 is a color screen display in which the Graphs and Stacked tabsare open to display the PIDS for the 2000 Toyota 4Runner in graph formand the Control tab is open instead of the Info tab;

FIG. 10 is a color screen display showing the Sharp SHOOTER andVolumetric Efficiency tabs open to display volumetric efficiency testdata for the 2000 Toyota 4Runner, including the VE Chart and the VETable of the present invention;

FIG. 11 is another color screen display in which the Sharp SHOOTER andFuel Trim tabs are open to show the fuel trim readings at absolutethrottle position v. engine RPM for the 2000 Toyota 4Runner (data isonly displayed in the “Bank 1 (Fuel Trim 1)” chart as a Toyota 4Runneronly has one front O2 sensor);

FIG. 12 is a second color screen display showing the volumetricefficiency test data for the 2000 Toyota 4Runner after the mass air flowsensor (MAF) has been removed and cleaned;

FIG. 13 is a second color screen display showing the load charts (Bank 1(Fuel Trim 1)) for the 2000 Toyota 4Runner after the MAF has beenremoved and cleaned;

FIG. 14 is a color screen display with the Controls tab and the DTCs tabopen showing no DTC (diagnostic trouble codes) codes pulled for a 1999GMC Sierra;

FIG. 15 is a color screen display with the Info, the Sharp SHOOTER andVolumetric Efficiency tabs open for the 1999 GMC Sierra showing thevolumetric efficiency data;

FIG. 16 is a color screen display with the Sharp SHOOTER and Fuel Trimtabs open for the 1999 GMC Sierra to show the load charts (both Bank 1and Bank 2 because this vehicle has 2 front O2 sensors) before anyrepair;

FIG. 17 is a second color screen display for the 1999 GMC Sierra showingthe volumetric efficiency data after the catalytic converter wasreplaced;

FIG. 18 is a color screen display with the DTCs tab open for a 1999Dodge truck with a check engine light on;

FIG. 19 is a color screen display showing the Catalyst Eff tab open toshow the catalytic efficiency chart and data for the 1999 Dodge truck (a1999 Dodge truck only has one front O2 sensor before the catalyticconverter (O2B1S1), and one rear O2 sensor after the catalytic converter(O2B1S2));

FIG. 20 is another color screen display in which the catalyticefficiency charts show one good and one bad catalytic converter;

FIG. 21 is still another screen display showing two good catalyticconverters;

FIG. 22 is another color screen display with the Sharp SHOOTER andTemperature tabs open to illustrate the Temperature Charts andTemperature Table of the present invention;

FIG. 23 is a color screen display with the Sharp SHOOTER and Fuel Trimtabs open showing the fuel trim test on a 1999 GM 5.3 liter engine;

FIG. 24 is a color screen display with the Sharp SHOOTER and VolumetricEff tabs open showing the VE tests on the engine of FIG. 23;

FIG. 25 is a color screen display with the Sharp SHOOTER and SimulatedInjector tabs open showing the test results on the engine of FIG. 23;

FIG. 26 is another color screen display related to the engine of FIG.23, with the Sharp SHOOTER and Power tabs open;

FIGS. 27-30 are a series of color screen displays (Fuel Trim, VolumetricEff, Simulated Injector and Power) on a 1999 GM 5.3 liter engine with anair leak;

FIGS. 31-34 are another series of color screen displays (Fuel Trim,Volumetric Eff, Simulated Injector and Power) on a 1999 GM 5.3 literengine with low fuel pressure;

FIGS. 35-38 are yet another series of screen displays (Fuel Trim,Volumetric Eff, Simulated Injector and Power) for a GM 5.3 liter enginewhich is running properly;

FIG. 39 A-I is a series of flow charts illustrating the operation of theanalysis tool of the present invention in the automated test mode,namely, KOEO then KOEC and then KOER; and

FIG. 40 is a screen display with the Digital and MultiTool tabs open.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 1 and 2, analysis tool 11, hardware wise amicroprocessor such as a laptop computer, includes a screen 13 which isdivided into an alert light indicator display 15 and a data display 17.Display 15 includes tabs “Controls”, “MultiTool”, “Info” and “?”.Display 17 has top level tabs “EScan”, “DTCs”, “Monitors”, “PIDs”,“Digital”, “Graphs”, “Mode 6”, “O2” and “Sharp Shooter”. Each of thetabs is associated with a particular screen display (e.g., FIG. 2) or aset of second level tabs and associated screens (e.g., FIG. 10), whichis activated by the mouse (not shown) of the laptop. In FIG. 2, the Infoand Digital tabs have been clicked on to open the associated screens.With reference to FIG. 9, clicking on the Graphs tab gives the user thechoice of three types of displays “Stacked”, “Dual/Combo” (not shown),and “Measure” (also not shown). The Dual/Combo screen allows thetechnician to chart up to 4 sensors (B1S1, B2S1, LTFTB1S1 and LTFTB2S1).(As is evident from paragraphs such as [0051], [0053] and [0065], B1stands for Bank 1, S1 stands for Sensor 1, LTFT stands for long termfuel trim, etc.) These charts will be auto scaled, with the scalingbeing displayed on the left side of the screen. The Measure screenallows the technician to plot saved or live data and to apply zoomfeatures and measurements to the data being displayed. Further, as isevident from, for instance, FIG. 13, clicking on the Sharp Shooter tabgives the user the choice of six different screens, “Fuel Trim”,“Volumetric Eff” (for volumetric efficiency), “Simulated Injector”,“Power”, “Catalyst Eff” (for catalyst efficiency), “Temperature”, and“Auto Diag” (for automatic diagnosis).

Display 15, Info includes “Rich” lights, “Lean” lights, “Center” lights,“Control Problem” lights, and “Fuel Trim” lights. One set of theforegoing is provided for B1S1 (bank 1, sensor 1), the other for B2S1.B1S1 is the sensor O2 in front of the catalytic converter and is alsoreferred to herein as O2B1S1. B2S1 is for the second O2 sensor in frontof the vehicle's catalytic converter and is also referred to as O2B2S1.However, not all vehicles have such a second front sensor. The term bankrefers to a bank of cylinders in an engine (e.g., 4, 5 or 6 inlinecylinders are usually designated a bank; each side of a V8 or V6 is abank). In FIG. 2, the Info screen also includes “Bank to Bank FuelTrim”, “Time to Engine Temperature”, “Engine Vacuum”, “ChargingVoltage”, “MIL OFF” and “Monitors Complete”. In addition to the lights,each of the foregoing is associated with a window showing the actualvalue (e.g., “Temp(F) 183.20”). MIL stands for malfunction indicatorlight. In FIG. 2, the MIL OFF light is green indicating that there areno DTCs, which is also confirmed with the 0 in the “#Codes” box. TheControls screen (see FIG. 9) provides controls (activated by clickingthe mouse incorporated into the laptop) for clearing data, saving data,loading data, saving screen, and printing screen. The key strokes (e.g.,F1) refer to standard keyboard keys. The MultiTool screen (FIG. 40)provides links to other tools such as a gas analyzer. The ? tab, as wellas the ? buttons on the Info screen and the various data display screensopen help screens in display 15. The ? button on the Info screen islinked to information related to the Info screen. The ? button on eachdata screen is linked to information specific to the associated datascreen. The ? tab opens the immediately previously opened help screen.

With reference to FIG. 1, analysis tool 11 is connected to power traincontrol module (PCM) 21 via data link connector 23, interface 25 andcables 27 and 29. As is well known, interface 25 converts the protocolof tool 11 to the particular ID protocol used by the PCM. Onceconnected, tool 11 requests (via conventional software) and is providedwith the ID protocol of module 21 which will be one of the following: GMJ1850 VPW; Ford J1853 PWM; CAN 150 15765; KWP ISO 14230; and ISO 9141-2.VPW stands for variable pulse width; PWM for pulse width modulated; CANfor controller area network; and KWP for key word protocol.

Once the protocol is identified, tool 11 pulls all the PIDS availablefrom module 21. As those skilled in the art will appreciate, the numberof PIDS varies with vehicle make, model and year. The basic (i.e.,minimum) PIDS are set forth in Table I, below.

TABLE I ETC (engine coolant temperature) LTFTB1 (long term fuel trim,bank 1) Engine RPM MAP (manifold absolute pressure) or MAS (mass airflow) or both O2B1S1 (oxygen sensor, bank 1, sensor 1) O2 B1S2 (oxygensensor, bank 1, sensor 2) STFTB1 (short term fuel trim, bank 1)Calculated Load Vehicle Speed Sensor Ignition Timing Advance for #1Cylinder Intake Air Temperature Absolute Throttle Position

Tool 11 also acquires the voltage, either from power train controlmodule 21 or from DLC 23, or both, depending on the make, model and yearof the vehicle.

Table II sets forth all the generic (e.g., OBDII generic) PIDS currentlypotentially available.

TABLE II Supported PIDS 0x01-0x20 (Status Query) Monitor Status SinceDTCs Cleared DTC that Caused Required Freeze Frame Fuel System 1 & 2Status Engine Coolant Temperature Short Term Fuel Trim Bank 1 Long TermFuel Trim Bank 1 Short Term Fuel Trim Bank 2 Long Term fuel Trim Bank 2Fuel Rail Pressure (Gauge) Intake Manifold Absolute Pressure Engine RPMAir Flow Rate from Mass Air Flow Sensor Commanded Secondary Air StatusLocation of Oxygen Sensors (2 Banks, 4 Sensors Each) O2 Bank 1 Sensor 1O2 Bank 1 Sensor 2 O2 Bank 1 Sensor 3 O2 Bank 1 Sensor 4 O2 Bank 2Sensor 1 O2 Bank 2 Sensor 2 O2 Bank 2 Sensor 3 O2 Bank 2 Sensor 4 OBDRequirements to Which Vehicle is Designed Location of Oxygen Sensors (4Banks, 2 Sensors Each) Auxiliary Input Status Time Since Engine StartSupported PIDS 0x21- 0x40 (Second Status Query) Distance Traveled WhileMIL is Activated Fuel Rail Pressure Relative to Manifold Vacuum FuelRail Pressure Bank 1 Sensor 1 (Wide Range O2S) (V) Bank 1 Sensor 2 (WideRange O2S) (V) Bank 1 Sensor 3 (Wide Range O2S) (V) Bank 1 Sensor 4(Wide Range O2S) (V) Bank 2 Sensor 1 (Wide Range O2S) (V) Bank 2 Sensor2 (Wide Range O2S) (V) Bank 2 Sensor 3 (Wide Range O2S) (V) Bank 1Sensor 4 (Wide Range O2S) (V) Commanded EGR EGR Error CommandedEvaporative Purge Fuel Level Input Number of Warm-ups Since DTCs ClearedDistance Since Diagnostic Trouble Codes Cleared Evap System VaporPressure Barometric Pressure Bank 1 Sensor 1 (Wide Range O2S) (mA) Bank1 Sensor 2 (Wide Range O2S) (mA) Bank 1 Sensor 3 (Wide Range O2S) (mA)Bank 1 Sensor 4 (Wide Range O2S) (mA) Bank 2 Sensor 1 (Wide Range O2S)(mA) Bank 2 Sensor 2 (Wide Range O2S) (mA) Bank 1 Sensor 3 (Wide RangeO2S) (mA) Bank 1 Sensor 4 (Wide Range O2S) (mA) Catalyst TemperatureBank 1, Sensor 1 Catalyst Temperature Bank 2, Sensor 1 CatalystTemperature Bank 1, Sensor 2 Catalyst Temperature Bank 2, Sensor 2Supported PIDS 0x41-0x60 (Third Status Query) Monitor Status thisDriving Cycle Control Module Voltage Absolute Load Value CommandedEquivalence Ratio Relative Throttle Position Ambient Air TemperatureAbsolute Throttle Position B Absolute Throttle Position C AcceleratorPedal Position D Accelerator Pedal Position E Accelerator Pedal PositionF Commanded Throttle Actuator control Minutes run by the Engine whileMIL Activated

The number of PIDS available from Table II depends on the make, modeland year of the vehicle. In operation tool 11 queries the vehicles PCMto determine which of the first 20 PIDS are, in fact, supported. Thosewhich are available are pulled. Thereafter, tool 11 queries the PCM todetermine which of PIDS 21-40 are supported. Again, those which areavailable are pulled. Finally, tool 11 queries the PCM to determinewhich of PIDS 41-60 are available and pulls those that are supported.The PID values are actually hexadecimal as indicated by “0x” (e.g.,0x21-0x40).

While the PIDS in the foregoing tables are both generic (e.g., OBDIIgeneric), there are enhanced PIDS and codes (e.g., OBDII enhanced) whichare also available on vehicles that could be used with the presentinvention.

As is evident from FIG. 1, unprocessed PID data can be displayed onscreen 17 as slide bars (as illustrated in FIG. 2) or as a graph with adigital readout (as illustrated in FIG. 3). In FIG. 3, for instance:“ECT” stands for engine coolant temperature; “LONGFTB1”, for long termfuel trim, bank 1; “LONGFTB2”, for long term fuel trim, bank 2; “MAP”for manifold absolute pressure; “RPM” for engine revolutions per minute;“O2B1S1”, O2 sensor, bank 1, sensor 1; “FTB1S1” for short term fueltrim, bank 1; and “O2B2S1”, for O2 sensor, bank 2, sensor 1.

From the generic PIDS (Tables I & II), tool 11 calculates and displays18 Calculated PIDS. Tables III and IV set forth these PIDS and theassociated methods for their determination.

TABLE III CALCULATED PIDS METHOD Bank 1 Total Trim Select LTFTB1. SelectO2B1S1 sensor. Add LTFTB1 to STFTB1. Bank 2 Total Trim Select LTFTB2.Select O2B2S1 sensor. Add LTFTB2 to STFTB2. Query PCM to see if B2S1 PIDis enabled. Must have B2S1 to calculate this PID. Cross Counts B1S1Program counts how many times per second (Hz) the O2B1S1 voltage crosses0.45 volts. The result will be greater or less than zero depending onwhat the cross count rate is. Select O2B1S1 sensor. Each time O2 voltagecrosses 0.45 v add 1 count. Add counts together for a period of 1 sec.Cross Counts B2S1 Program counts how many times per second (Hz) theO2B2S1 voltage crosses 0.45 volts. The result will be greater or lessthan zero depending on what the cross count rate is. Select O2B2S1sensor. Each time O2 voltage crosses 0.45 v add 1 count. Add countstogether for a period of 1 sec. Query PCM to see if this PID is enabled.Must have B2S1 PID to calculate this PID. Cross Counts B1S2 Programcounts how many times per second (Hz) the O2B1S2 voltage crosses 0.45volts. The result will be greater or less than zero depending on whatthe cross count rate is. Select O2B1S2 sensor. Each time O2 voltagecrosses 0.45 v add 1 count. Add counts together for a period of 1 sec.Cross Counts B2S2 Program counts how many times per second (Hz) theO2B2S2 voltage crosses 0.45 volts. The result will be greater or lessthan zero depending on what the cross count rate is. Select O2B2S2sensor. Each time O2 voltage crosses 0.45 v add 1 count. Add countstogether for a period of 1 sec. Query PCM to see if this PID is enabled.Must have B2S2 PID to calculate this PID. Engine Vacuum Select MAPsensor. Select Barometric Pressure. Subtract Barometric Pressure fromAbsolute Manifold Pressure. Engine Running Time Select RPM. Monitor RPMcount higher than 0 RPM against a timer. B1 Fuel Control Monitor SelectO2B1S1 Sensor. Time O2 Voltage above 0.45 v (rich). Time O2 voltagebelow 0.45 v (lean). Read out % rich, % lean. B2 Fuel Control MonitorSelect O2B2S1 Sensor. Time O2 Voltage above 0.45 v (rich). Time O2voltage below 0.45 v (lean). Read out % rich, % lean. Query PCM to seeif this PID is. Must have B2S1 PID to calculate this PID. Bank 1 to Bank2 Add LTFTB1 to LTFTB2. Query PCM to see Fuel Trim if B2S1 PID isenabled. Must have B2S1 PID to calculate this PID. Catalyst EfficiencyUse catalyst efficiency algorithm as set forth below. Bank 1. CatalystEfficiency Use catalyst efficiency algorithm as set forth below. Bank 2.Query PCM to see if this PID is enabled. Must have B2S1 PID to calculatethis PID. Voltage at DLC Monitor voltage at DLC. Closed O2 Loop Status 1Get O2 status from PID. Closed O2 Loop Status 2 Get O2 status from PID.Theoretical Air Flow Select RPM, MAS (grams/sec.) and ATP. VolumetricEfficiency Select RPM, MAS (grams/sec.) and ATP. Percent

In the above table, the O2B1S1 PID includes STFTB1.

TABLE IV Calculated PIDS Name Abbrev Units Actual PIDS NeededComputation Bank 1 Total Trim Total Trim B1 % STFT1, LTFT1 [STTF + LTFT]Bank 2 Total Trim Total Trim B2 % STFT2, LTFT2 [STFT + {grave over( )}LTFT] Cross Counts e O2Cross11 Hz O2B1S1 O2 voltage crosses 0.45 v,O2B1S1 Hysteresus 0.05 V Cross Counts e 02Cross21 Hz O2B1S2 O2 voltagecrosses 0.45 v, O2B2S1 Hysteresus 0.05 V Cross Counts O2Cross12 HzO2B2S1 O2 voltage crosses 0.45 v, O2B1S2 Hysteresus 0.05 V Cross Counts02Cross22 Hz O2B2S2 O2 voltage crosses 0.45 v, O2B2S2 Hysteresus 0.05 VEngine Vacuum Vacuum HG MAP, RPM, BARO BARO − MAP Engine Running RunTimeS RPM Time RPM > O Time Fuel Control FCtrlMonB1 % O2B1S1 Rich if > 0.45V [(Time Monitor Bank1 Rich − Time Lean)/Tot Time)] * 100 = [2 * Trich −Ttime)/Ttime)] * 100 Fuel Control FCtrlMonB2 % O2B2S1 Rich if > 0.45 V[(Time Monitor Bank2 Rich − Time Lean)/Total Time)] * 100 = [2 * Trich −Ttime)/Ttime)] * 100 Bank 1 to Bank 2 BtoBFT % LTFTB1, LTFTB2 LTFTB1 +LTBTB2 = Bank Fuel Trim to Bank Fuel Trim Catalyst Efficiency CatEffB1 %O2B1S1, O2B1S2, RPM See CAT EFF (Catalytic Bank1 Efficiency) Paragraph[0086] Catalyst Efficiency CatEffB2 % O2B2S1, O2B2S2, RPM See CAT EFF(Catalytic Bank2 Efficiency) Battery Voltage at DLC BatteryV V Voltageat DLC Closed O2 Loop 1 ClosedLp1 On FUELSYS1 Fuel System 1 & 2 StatusStatus 1 Off Closed O2 Loop 2 ClosedLp2 On FUELSYS2 Fuels System 1 & 2Status Status 2 Off Theoretical Air Flow TAF g/s MAS, RPM, ATP TAF =(RPM/120) * AirDen (air density) * AltCorn (altitude correction)Volumetric VE % % MAS, RPM, ATP AVF (actual volumetric EfficiencyPercent efficiency)/TAF * 100%

BARO stands for barometric pressure. In most vehicles this informationcomes from the MAP sensor. Some vehicles (e.g., Cadillac) have aseparate barometric pressure sensor. Theoretical Air Flow (TAF) is howmuch air an engine could pump at 100% efficiency. Voltage at DLC, ClosedO2 Loop Status 1 and Closed O2 Loop Status 2 are included in theforegoing two tables even though they are not calculated PIDS as theinformation which they provide needs to be considered with thecalculated PIDS. The foregoing calculated PIDS (Battery Voltage at DLCand Closed O2 Loops 1 & 2 being treated as such) are illustratedschematically in FIG. 1 as CPID 1-18.

In operation, once connected to DCL 23 via interface 25, tool 11automatically selects from the available PIDS those which will activatethe lights on display 15 and automatically enables the Info tab. If theparticular vehicle being diagnosed does not have a bank 2 sensor 1 O2sensor, the B2S1 lights will not be activated and will remain grey as isevident from the drawings (e.g., FIG. 4). The other lights areautomatically lit depending on the value of read PIDS vs. Break Point(BP) values or an Algorithm (A), as set forth in Table V. The languagein quotes corresponds to the nomenclature illustrated in display 15 inthe various screen displays (e.g., FIG. 2).

TABLE V Break Point (“BP”) or Algorithm Light (“A”) Description The“Rich” Indication BP If the oxygen sensor voltage is greater than AlertLight 0.45 v, the light will be activated yellow. This indicates theair/fuel ratio is less that 14.7 to 1 or rich. The “Lean” Indication BPIf the oxygen sensor voltage is less than 0.45 v, Alert Light the lightwill be activated blue. This indicates the air/fuel ratio is greaterthan 14.7 to 1 or lean. The “Center” Indication A If the oxygen sensor'svoltage is both greater Alert Light than 0.55 v and less than 0.35 v andis cycling at the proper frequency evenly between rich and lean air/fuelmixtures, then the light will be activated green. This is an indicationthat the fuel control system has good control over fuel delivery and itis maintaining a 14.7 to 1 air/fuel ratio. If the rich and lean lightsare active but the center light is not turned on then the fuel controlsystem does not have good delivery. The Fuel “Control A If the fueldelivery system has failed to control Problem” Indication the properair/fuel ratio, the light will be Alert Light activated red. If the fueldelivery system has failed for longer than 15 seconds, then the red fuelcontrol problem light will begin flashing. The “Fuel Trim” BP If thelong term fuel trim is less than +/−10%, Indication Alert Light thelight will be activated green. If the long term fuel trim is between+/−10% and +/−13%, the light will be activated yellow. If the long termfuel trim is between +/−13% and +/−20%, the light will be activatedorange and the light will be activated red when the long term fuel trimis greater than +/−20%. The “Bank To Bank BP If the long term fuel trimfrom bank one and Fuel Trim” Indication bank two is +/−5%, the lightwill be activated Alert Light green. If the long term fuel trim frombank one and bank two is between +/−5% and +/−8%, the light will beactivated yellow. The light will be activated orange when the long termfuel trim is between +/−8% and +/−10%. The light will be activated redif it is greater than +/−10%. “Time To Engine A If during engine warm upthe temperature is slow Temperature” Alert (Deg F./sec < 0.05) toincrease, the light will be Light activated yellow. If during warm upthe operating temperature of the engine is not achieved in apredetermined time, the light will turn red, indicating the time toengine temperature has failed. If the engine overheats, the light willturn red and flash indicating that the engine is overheated. When thecoolant has reached the point when the thermostat opens the display willchange and alert the technician that the thermostat has been opened. Ifthe thermostat fails to open or there is a flow problem the light willturn color. Existing cooling system problems may be indicated by furtherwatching the temperature. Engine Coolant Range/Overall calculation forInfo tab: StartDeg = Temperature that engine starts at (Deg F.) StartSec= Time that engine starts (sec) Deg F./sec = Present Temperature(F.)/Time Since Engine Started (sec) Before reaching 190 F. (not warmedup yet): Yellow if warming too slow (<0.05 Deg F./Sec) Blue if OK or ifduring 1^(st) 40 seconds of warmup Orange if warming too fast (>0.40 DegF./Sec Red if overheated (T > 240 F.) After reaching 190 F.: Red ifoverheated, or if time to 190 F. < 0.05 Deg F./Sec, or >0.40 Deg F./SecGreen if OK (T between 190 F. and 240 F. and warmup time OK) “EngineVacuum” Alert BP This will only be active if the engine is equippedLight with a MAP sensor. With the key on and the engine off, the lightwill indicate the barometric pressure. If the barometric pressure sensormisreads, the light is turns red with the message “Baro Misreading”. Ifthe barometric pressure is correct, the light will be green with themessage “Baro Good”. The cranking vacuum is checked when the engine isturned over for 3 seconds. If it is greater than 1″ HG, the light turnsgreen with the message “Cranking Vacuum Good”. If the reading is lessthan 1″ HG, the light is turned red with the message “Cranking VacuumBad”. Once the engine is running, a calculation is done that comparesthe engine vacuum to the barometric pressure. If the engine has goodvacuum, the alert light is turned green with the message “Engine VacuumGood”. If the engine vacuum is slightly low, the alert light is turnedyellow with the message “Engine Vacuum Low”. If the engine vacuum islow, the alert light is turned red with the message “Engine Vacuum Low”.If there is no MAP sensor this light is not illuminated. See, forinstance, FIG. 4. Battery “Charging BP If the battery open circuitvoltage is low, the Voltage” Alert Light light is turned red with themessage “Battery Voltage Low”. If the battery open circuit voltage isgood, the light is turned green with the message “Battery Voltage Good”.If the battery open circuit voltage is high, the light is turned redwith the message “Battery Voltage High”. During cranking, the crankingvoltage is checked. If the cranking voltage is low, the battery voltagealert light is turned red with the message “Cranking Voltage Low”. Ifthe cranking voltage is good, the battery voltage alert light is turnedgreen with the message “Cranking Voltage Good”. Once the engine isrunning, the battery voltage alert light monitors the charging system.If the charging system has low voltage, the battery voltage alert lightis turned red with the message “Charging System Voltage Low”. See, forinstance, FIG. 6 . If the charging system has good voltage, the batteryvoltage alert light is turned green with the message “Charging SystemVoltage Good”. See, for instance, FIG. 4. If the charging system hashigh voltage, the battery voltage alert light is turned red with themessage “Charging System Voltage High”. Malfunction Indicator Counter Ifno diagnostic trouble codes are present, the Light (“MIL”) Alert lightis turned green, the message “MIL OFF” Light (No DTCs) displayed, withthe number ‘0’ displayed. If there are diagnostic trouble codes, thelight is turned red with the number of diagnostic trouble codes (DTC)present displayed. For example, if there is 1 DTC present the light isturned red and the number 1 displayed. See FIG. 18. If there are codespresent but the PCM did not request for the MIL to be lit the light willbe yellow. If the PCM requests for the MIL to be turn on the light willbe red. “Monitor” Light BP If all monitors have run the monitor light isGreen #0. If monitors have not run the monitor light is red with numberof monitors not run listed.

The various Break Points, algorithms and the counter identified aboveare schematically illustrated in FIG. 1 as: boxes BP1-BP7; boxes A1-A3;and box C.

In order for the technician or the automated diagnostic system tocorrectly diagnose the car, several additional, novel tests and chartshave been developed. These consist of fuel trim, engine volumetricefficiency, simulated injector, power, catalyst efficiency, and enginecoolant range. In the drawings (e.g., FIG. 11) the screen tabs aredesignated, respectively: “Fuel Trim”, “Volumetric Eff”, “SimulatedInjector”, “Power”, “Catalyst Eff”, and “Temperature”. The last secondlevel tab on the right, “Auto Diag”, is discussed below.

Fuel Trim Charts

When an engine is originally programmed, a linear equation from idle towide open throttle is written by the manufacturer. However, since noengine has a linear air flow curve, fuel delivery based on such a linearmodel is adjusted by the manufacturer by what is known as a fuel mappingtable, which is programmed into the PCM. In the operation of a vehicle,if all the PCM's calculations (based on sensor inputs) are correct, theinjector on time based on the mapping table will not need to be changed.Thus, what is known as fuel trim will remain at or close to ‘0’. If thePCM calculations are off the injector on time will automatically beadjusted to add or subtract fuel so that the air/fuel ratio will remainat 14.7 air to 1 fuel for all engine speeds. This shift that is createdby the feedback system is given to the technician as fuel trim (e.g.,the LTFT PID, the STFT PID). If the long term trim (LTFT) exceeds+/−10%, it is recommended that the vehicle's fuel control system berepaired.

The Fuel Trim Charts of the present invention, such as illustrated inFIGS. 11, 13, and 16, are the technician's window into the PCM's fueldelivery program. To make sense of the raw fuel trim data from the PCM(e.g., put it in perspective), the Fuel Trim Chart is broken up intocells which represent Absolute Throttle Position (ATP; sometimesreferred to as just TP) against RPM. The ATP represents the load on theengine. As the engine speed increases (both RPM and ATP increase) thePID data (e.g., LTFTB1) from the PCM is assigned to different cells. Atthe same time the amount of fuel trim (as described below) is assigned aparticular color. In operation the vehicle should be, but does not haveto be, taken on a test drive and the cells are filled between idle andwide open throttle (WOT).

PIDS monitored to fill the Fuel Trim Chart: RPM, ATP, LTFTB1, STFTB1 andLTFTB2 (if available). The LTFTB2 PID does not have to be monitored butis needed to fill the second chart labeled “Bank 2 (Fuel Trim 2)”. TheSTFTB1 or B2 is needed when checking fast changes to the fuel control,or where total trim or LTFT has been cleared. Cells on the chart willfill according to RPM and ATP and the following color code. (Cells willnot fill during deceleration.)

-   -   Green: FT (fuel trim) between −10 and +10    -   Yellow: FT between −13 and −10 OR between +10 and +13    -   Orange: FT between −20 and −13 OR between +13 and +20    -   Red: FT less than −20 OR greater than +20        As is evident from the figures, the Charts not only indicate the        appropriate color, but also the positive (+) or negative (−)        character. The application of this Chart to specific power plant        problems is discussed below. See, for instance, FIG. 11 and the        associated discussion.        Volumetric Efficiency (VE)

An engine is an air pump that pumps air into the intake and out theexhaust. Measuring the engine's actual volumetric efficiency (or VE), orthe engine's actual ability to pump air, and comparing this actualefficiency with such engine's calculated VE can be used to indicate ifthere are problems with the mechanical condition of the engine (or theexhaust system) or the sensors used to read the air flow from theengine.

There are two air-fuel delivery systems used in modern vehicles. One isthe speed density system and the other is the mass air flow system.These two systems can be used to produce the same result, namely:measuring the actual weight of the air flowing into the engine (ingrams/sec.); and calculating a theoretical value (Calculated VolumetricEfficiency). These two systems use different sensors (the first is basedon the MAP sensor; the latter, on the MAS (a/k/a MAF sensor). Because ofthis different calculations are necessary, as discussed below inreference to FIG. 10. While the results from these tests will beinterpreted differently, the same information will be displayed on thescreens.

The speed density system calculates the air flow to the engine bymeasuring the vacuum and multiplying this by the RPM, liter size of theengine, intake air temperature, and volumetric efficiency percent (thepercentage TAF (theoretical air flow), as indicated by the red traces onthe VE Charts, is multiplied by to get Calculated VolumetricEfficiency). The vacuum is measured by the manifold absolute pressuresensor (MAP). This sensor measures the difference in pressure betweenthe barometric pressure and the intake manifold pressure. Thus, the PIDthat is read by tool 11 gives the absolute pressure within the manifold,not the intake manifold vacuum. As the throttle plate is opened thepressure differential between the barometric pressure and intakemanifold pressure decreases. Thus, the MAP reading becomes closer to thebarometric pressure reading. Since this MAP reading is what sets thefuel delivery of the engine (via injector on time), this reading can beput into a chart that will display the actual (assuming the sensor isnot malfunctioning or misreading) grams per second of air flowing intothe engine or the actual volumetric efficiency of the engine. This isthe yellow trace on the VE Chart (e.g., FIG. 10). Further, if the actualVE reading is compared against a calculated VE reading (as describedbelow) for the same engine, it can be determined if the engine (or theexhaust system) has a mechanical problem or if the MAP sensor itself hasa failure.

This Calculated VE will be looked up from a VE Lookup Table (not shown)stored in tool 11 that uses the PID for the Absolute Throttle Positionagainst the RPM to determine what the MAP sensor should read. The PIDSmonitored to fill the Lookup Table, the VE Chart and the VE Table (%Diff Actual v. Calculated) are: RPM and MAP. The information needed tobe entered is: liters (engine size), ambient air temperature, andElevation (Feet Above Sea Level). Vacuum is barometric pressure (BARO)minus absolute pressure at sea level. The vacuum at idle is about 20″ HGat sea level; about 15″ HG at 5,500 ft. above sea level. However, theabsolute pressure is the same at both elevations, namely, about 26-30kpa at hot unloaded idle.

The Calculated VE from the MAP sensor is determined as follows(IAT=intake air temperature; TAF=theoretical air flow):

-   -   If Lookup Value based on Throttle Position>=0, use Lookup Val    -   If Lookup Value based on Throttle Position<=0, use BARO+Lookup        Val        AirDens=353.155635/(AirDegC+273.15)(This shows how air temp        modifies the equation.)        IATmx=AirDens/1.184        AirFlow=RPM/60*Liters/2*MAP*0.01*IATmx*VEmx    -   TAFNoCorr: Same as above only does not use VE multipler (VEmx)        (Used for the Calc Pids.)    -   RPMEff (RPM Efficiency): 0.7 for 0-1000 RPM; 0.8 for 1000-1500        RPM; 0.9 1500-2000 RPM; 0.95 for 2000-3000 RPM; 0.95 for        3000-4000 RPM; and 0.95 for >4000 RPM.

The MAS sensor reads the air mass entering the engine directly. Tocalculate the VE with this sensor the liter size of the engine,barometric pressure, and intake air temperature must be known. If thesevariables are set correctly then both the actual and the calculated VEcan be determined.

When using the MAS sensor the calculated VE is based on the following.The PIDS monitored to fill the VE Chart and VE Table are: RPM, MAS(a/k/a MAF) and ATP. The information needed to be entered is: liters(engine size), ambient air temperature and Elevation (Feet Above SeaLevel). The VE Calc (VE Calculation) is as follows:

-   -   AltCorn (Altitude Correction): 1-(Alt/29900).    -   RPMEff (RPM Efficiency): 0.7 for 0-1000 RPM, 0.8 for 1000-1500        RPM, 0.8 1500-2000 RPM, 0.8 for 2000-3000 RPM, 0.85 for        3000-4000 RPM, 0.8 for >4000 RPM.    -   TP/VE Corrections at >50% TPS: 0% TPS=21.0%, 10% TPS=24.0%, 20%        TPS=34.0%, 30% TPS=61.0%, 40% TPS=75.0%, 50% TPS=80.0%. Equation        linear between set points.    -   Greater than 50% throttle: VE        Calc−Liters*(RPM/120)*1.184*RPMEff*AltCorn.    -   Less than 50% throttle:        vecALC=[Liters*(RPM/120)*1.184*RPMEff*AltCorn]*TP/VE Correction        at <50% throttle.    -   Compare VECalc and MAP (Actual grams Per Second from PCM        computer).    -   PercDiff (Percentage Difference between calculated and        MAF)=(VECalc−MAF)/(MAF)*100.        Simulated Injector

The fuel injection system is about air flow and fuel flow. The airflowing into the engine is unknown and, therefore, must be equated for.Sensors (MAP or MAF, IAT, RPM, BARO) positioned in the induction systemof the engine report vital information to the PCM which then uses thisinformation to equate the air flowing into the engine by weight in gramsper second (g/s). Once the air is known the proper amount of fuel byweight will be metered into the air. In most conditions this targetedair/fuel mixture is 14.7 lbs. of air to 1 lb. of fuel or 14.7 to 1. (Formaximum power this air/fuel ratio will be approximately 12.5 to 1.)Unlike the air entering the engine, the amount of fuel being deliveredto each cylinder is known. If the injector is a 5 lb. per hour injector,0.036 grams per millisecond of injector on time will be delivered. Sincethis fuel rate is a known value no equation will be necessary.

If the PCM receives the correct sensor inputs (MAF or MAP, IAT, RPM,BARO) it will equate the correct air by weight entering the engine. Itwill then deliver the correct weight of fuel to the air. The engine willthen burn the air/fuel mixture in the combustion process. As the burnedair/fuel mixture is exhausted from the engine the oxygen sensor (e.g.,O2B1S1) will check for the correct air/fuel ratio. If the mixture iscorrect there will be no fuel correction. This means the base airequation programmed into the PCM by the manufacturer will be multipliedby 1. However, if the mixture is incorrect the PCM will make acorrection to the base air equation. If the air/fuel ratio is lean thebase air equation will be multiplied by a number greater than 1 (e.g., amultiplier of 1.2 would increase the injector on time by 20%). If theair/fuel ratio is rich the base air equation will be multiplied by anumber less than 1 (e.g., a multiplier of 0.8 would decrease theinjector on time by −20%). This multiplier is referred to as fuel trim.The fuel trim is part of the feedback system that is in place to keepthe air/fuel ratio at a target value determined by the PCM.

When this multiplier is greater than +/−10% a problem is indicated thatwill require repair. It would be desirable for a test to be run thatwould indicate where the problem is located in the fuel injectionsystem. This is accomplished by a test sequence, referred to as theSimulated Injector, by taking the actual air flow given in grams persecond and the calculated air flow given in grams per second and puttingthese values into the simulated injector equation of the presentinvention. The simulated injector equation takes the known value of theinjector flow rate in lbs per hour and divides it into the air flow ingrams per second. (A 1 lb/hr injector flow rate would equal 0.007 gramsof fuel per millisecond of injector on time. If an injector flow rate of5 lbs/hr were used the fuel injector would flow 0.036 grams of fuel perms of injector on time.) By comparing the difference between the actualinjector on time and the calculated injector on time a problem can belocated. The location of the problem can be determined due to the fueldelivery system (injectors and fuel pressure) being constant. If theinjector or fuel pressure varies, the fuel trim will have to compensatefor this variation. This additional fuel trim will alter the base airequation. In this condition the actual injector on time will bedifferent than the calculated injector on time. When the calculatedinjector on time and actual injector on time vary this is an indicationthe fuel delivery system is at fault. If the engine sensors miss read,the fuel trim will alter the base air equation so the air to fuel weightare corrected. Comparing the actual injection on time with thecalculated injection on time will show that the injector on times matchvery closely to one another. This is an indication that the problem isin the sensors.

Actual injector on time is determined as follows:Revolutions per minute/60 seconds=Revolutions per second(RPS)Revolutions per second/4=Strokes per second(SPS)Actual air flow in grams/second divided by air/fuel ratio=Fuel rate(FR)Fuel rate divided by injector flow rate=Milliseconds of injector on timeMilliseconds of injector on time+1 millisecond injector turn ontime=Injector on timeInjector on time×fuel trim=Actual injector on time

Calculated injector on time is determined as follows:Revolutions per minute/60 seconds=Revolutions per second(RPS)Revolutions per second/4=Strokes per second(SPS)Calculated air flow in grams/second divided by air/fuel ratio=Fuelrate(FR)Fuel rate divided by injector flow rate=Milliseconds of injector on timeMilliseconds of injector on time+1 millisecond injector turn ontime=Calculated Injector on time

By comparing the difference between the actual injector on time (whichequates fuel trim) and calculated injector on time (which has no fueltrim equation), the vehicles fuel injection problem(s) can clearly beseen. If the problem is located in the vehicle's sensors (MAF or MAP,BARO, RPM, IAT, ECT, O2) the fuel trim will adjust the actual injectoron time so that it is equal to the calculated injector on time. If theproblem is in the fuel delivery system the fuel trim will adjust theactual injector on time so that it is different than the calculatedinjector on time.

EXAMPLE 1

1999 GMC 5.3 liter engine with the air boot leaking bypassing the massair sensor, which allows the mass air sensor to misread the air enteringthe engine.

VI Injector=5 lb per hour.

Actual Injector on Time:3480RPM÷60 sec=58RPS58RPS÷4=14.5SPSActual air rate 105GPS÷1405SPS=7.24GPS7.24GPS÷14.7AF=0.492FR0.492FR÷0.036 injector flow rate=13.68 ms13.68 ms+1 ms injector turn on time=14.68 ms14.68 ms×1.186FT=17.41 ms actual injector on timeCalculated Injector on Time:3480RPM÷60 sec=58RPS58RPS÷4=14.5SPSCalculated air rate 127.5GPS÷1405SPS=8.79GPS8.79GPS÷14.7AF=0.598FR0.598FR÷0.036 injector flow rate=16.61 ms16.61 ms+1 ms injector turn on time=17.61 ms17.61 ms×1FT=17.61 ms calculated injector on timeInjector on time difference=0.2 ms. The percentage difference is 1.12.This indicates that the problem is a MAF sensor misreading.

EXAMPLE 2

2001 Malibu 3.1 liter engine; purge control making fuel system rich;fuel problem;

VI Injector=5 lb per hour

Actual Injector on Time:3500RPM÷60 sec=58.33RPS58.33RPS÷4=14.58SPSActual air rate 34.87GPS÷14.58SPS=2.39GPS2.39GPS÷14.7AF=0.162FR0.162FR÷0.036 injector flow rate=4.51 ms4.51 ms+1 ms injector turn on time=5.51 ms5.51 ms×0.8FT=4.40 ms actual injector on timeCalculated Injector on Time:3500RPM÷60 sec=58.33RPS58.33RPS÷4=14.58SPSCalculated air rate 33.88GPS÷14.58SPS=2.32GPS2.32GPS÷14.7AF=0.158FR0.158FR÷0.036 injector flow rate=4.39 ms4.39 ms+1 ms injector turn on time=5.39 ms5.39 ms×1FT=5.39 ms calculated injector on timeInjector on time difference=0.99 ms. The percentage difference is 18.This would indicate that the problem is in the fuel delivery system.

If enhanced data is available (e.g., OBDII enhanced) the SimulatedInjector value would correspond to the actual injector on time given bythe PCM as a PID If the engine injector size is known, the calculationwould give the actual injector on time of the engine. This actual PIDvalue could be compared to a calculated injector on time and thedifference would indicate where the problem is located in the injectionsystem.

Power

It is desirable to know how much power an engine can produce. This canbe used to detect if the engine can make its rated horsepower or theengine has low power. If the difference between actual horsepower andcalculated horsepower can be determined, whether the engine's power iscompromised or not can also be determined. In order to calculate thehorsepower output of an engine the air flow rate in grams per second isused. An air flow rate of about 6 lbs/hour produces 1 horsepower ofusable mechanical power at the flywheel of the engine. The air/fuelratio will change this available power at the flywheel. (An air/fuelratio of 12.5 to 1 produces more horsepower than an air/fuel of 14.7 to1.) The power equation set forth below assumes that all the mechanicalparts of the engine, including ignition timing, are functioningcorrectly in order for the calculated horsepower to correctly be equatedto the actual horsepower.

Horsepower Equation:HP=air flow lb/hr÷2721.54 gram force.

-   -   Since air flow problems can be corrected by fuel trim, the fuel        trim (FT) will be multiplied by the horsepower.    -   Total Horsepower Equation: Total horsepower=FT×HP.        Catalyst Efficiency Test

The Catalyst Efficiency Test, illustrated in FIGS. 19-21, is a way thetechnician can confirm the present operation of a vehicle's catalyticconverter. When testing the converter, it is important for the operatingconditions to be correct before a judgment is passed on the condition ofthe catalytic converter. To test the operating conditions of the fuelcontrol system, the “Prepare Test (Calculate Below)” button is pushed(top center of screen 17 in, for instance, FIG. 19). The button willturn green notifying the technician that the testing sequence has begun.All of the indication lights set forth below must turn from red to greenfor the results of this test to be accurate. However, the test can berun at any time by pushing the “Start Test” button in the middle of thescreen (once pushed, the button reads “Testing” as illustrated).

-   -   The DTC Indication Light: The vehicle's PCM must not have any        DTC's or pending codes available in order for this light to turn        green.    -   The Fuel System Indication Light: The vehicle's PCM must be in        control of the fuel system in order for this light to turn        green.    -   The Fuel Trim Indication Light: The vehicle's PCM must have the        long term fuel trim functioning between +/−10% in order for the        light to turn green.    -   The Coolant Temperature Indication Light: The engine coolant        temperature must be higher than 170° F. in order for the light        to turn green.    -   The RPM Indication Light: The engine RPM must be held greater        than 1800 for at least 1 minute in order for the light to turn        green.    -   The Rear O2 Indication Light: The rear O2 sensor must be active        and move rich to lean with the fuel system conditions in order        for the light to turn green. As indicated on the screen, during        the rear O2 test the technician is instructed to snap the        throttle several times. This will allow the converter to become        saturated and the rear O2 will follow the front O2 with a slight        delay. Checking the rear O2 sensor is important not only for the        catalyst efficiency, but also for the fuel control of the power        plant. It accomplishes this by changing the fuel trim value.        Note, however, if the vehicle has “Wide Range O2 sensors”, the        test will not perform correctly. Some vehicles misleadingly        reference a WRAF (wide range air fuel) sensor as a B1S1 sensor.        In such cases the data will not be correct and the test cannot        be performed.

Once all indication lights turn green, the catalyst efficiency test canbegin. It will take 20 seconds for the catalyst efficiency percent to bedisplayed in the window. Once the display has a digital reading thedisplay boarder will turn color to indicate the condition of thecatalytic converter. Green indicates a good converter. Yellow indicatesthat the converter is marginal. Orange indicates that the converter isgoing bad. Red indicates that the converter is compromised. To get thebest results from this test, the vehicle should be run in threeconditions: idle; high idle; and steady state curse. If the vehicle isbeing driven in stop and go traffic, the catalyst efficiency will dropto the 60% range with a good converter. Note: before the catalyticconverter is to be replaced the technician should always check the DTCsfor a catalyst efficiency code. If no code is present and the monitorshave run, the Mode 6 data on the catalyst efficiency should be checked.If it shows good, replacement of the catalytic converter will not fixthe vehicle unless it is restricted. If there is a code set and thecatalyst efficiency shows good, check for a TSB (technical servicebulletin from the manufacturer) on reprogramming the PCM.

The PIDS monitored to determine the Catalyst Efficiency and fill chartare: RPM, O2B1S1, O2B1S2, O2B2S1 and O2B2S2. Note that O2B2S1, O2B2S2are only needed for the BANK TWO calculations.

-   -   Bx=B1 for BANK ONE calculation or B2 for BANK TWO calculation.        AmpFront=O2BxS1 Maximum−O2BxS1 Minimum        AmpRear=O2BxS2 Maximum−O2BxS2 Minimum        Cat Eff %=(1−AmpRear/AmpFront)×100

Catalytic Efficiency Color Codes are as Follows:

-   -   Green: Cat Eff % greater than or equal to 80    -   Yellow: Cat Eff % between 70 and 79    -   Orange: Cat Eff % between 60 and 69    -   Red: Cat Eff % less than 60        Engine Coolant Range Chart

The cooling system is a very important part of the operation andfunction of the fuel injection system. When the engine is first startedthe engine is at ambient temperature. In these conditions the fuelinjection will need to add fuel or enrich the air/fuel mixture whichcould drop to about 10 to 1. In turn, this will increase the emissionsat the tail pipe. Due to tighter governmental regulations this isundesirable. It is desirable to warm the engine rapidly to operatingtemperature, about 200° F. to 225° F. Once the engine is at operatingtemperature the fuel control system will target an air/fuel mixture ofabout 14.7 to 1. This will substantially decrease the tailpipe emissionlevels. During the chemical reaction between the oxygen and hydrocarbonchains heat energy is released from the burning fuel. About 35% of thisheat energy is lost to the engine cooling system. The internalcombustion engine's cooling system is designed to take on heat, createdby this chemical reaction and the friction between the engine's movingparts, and exchange it into the ambient air. If the engine's coolingsystem cannot be maintained the emission levels rise at the vehicle'stailpipe. The mechanical parts of the engine can also be damaged in theevent of the cooling system not maintaining the coolant temperature. Dueto the importance of the cooling system upon the fuel injection andmechanical condition, it is desirable to have a test that checks thecooling system's function. The temperature chart in FIG. 22 is just sucha test. By monitoring the coolant temperature increase, the rate thatthe coolant takes on heat can be calculated. If this rate is on targetand obtains the correct operational temperature in a given time span,the coolant temperature sensor and cooling system are functioningproperly. However, if these do not change at an expected target valuethe cooling systems operation is not functioning to its design. Bymonitoring the coolant temperature, the coolant temperature rate ofchange and the vehicle's speed, the coolant system can be diagnosed.This diagnostic can take place by the technician viewing the chartsillustrated in FIG. 22 or an automated sequence of tool 11. Problems canbe diagnosed such as: thermostats sticking open or closed, radiator airflow restrictions, radiator coolant passage restrictions, blown headgaskets, low coolant levels, and cooling fans not working properly.

With regard to the Temperature tab, the chart plot contains: speed;temperature (Deg F); and rate (DegF/Sec). These values, plus TPS (%) arealso displayed digitally on the screen. The Temp (Deg F) also has aboarder around it showing the most recent color code. The colors forTemp background and table cells (same as info light):

-   -   Green: Warm-up Good    -   Yellow: Warm-up Too Slow    -   Orange: Warm-up Too Fast    -   Red: Overheated

With regard to the Temperature Table, the time for table fill can beselected as 2:30, 5:00, 10:00 or 15:00 (Min:Sec). This time is dividedinto 10 horizontal cells and ends up with 15, 30, 60, or 90 seconds percell. The vertical cells go from −40 to 260 Deg Fand are divided between10 sells (30 Deg F. per cell).

FIGS. 4-13 illustrate the use of the present invention in diagnosing a2000 Toyota 4Runner that was brought in for service for low power. FIG.4 illustrates the DTC codes that were pulled up, which indicate nonepresent, which does not assist in diagnostic. The Mode 6 data was thenread by tool 11 but, as is evident from the screen illustrated in FIG.5, no failure is indicated. Mode 5 (O2) data was then pulled from thePCM. As illustrated in FIG. 6, no fault is shown. The Monitors were thenchecked. However, as is evident from FIG. 7, no problems wereidentified. The data from the PIDS was again reviewed and graphed but,again, the problem could not be identified. See FIGS. 8 and 9. From thegraphs the fuel control of the vehicle looks good.

The volumetric efficiency test was then run. See FIG. 10. This testcalculates how much air the engine should pump (red trace) and comparesit to how much air the engine is actually pumping (yellow trace). Thecalculated and actual should be within +/−10% of each other. Thedifference between the actual VE and the calculated VE are also plottedon the VE table with colors and numbers to indicate the degree ofdifference. The VE Chart clearly shows that the engine's VE reading islower than expected. The possible causes are as follows:

-   -   Engine worn out.    -   Camshaft out of time with the crankshaft.    -   Intake restriction.    -   Exhaust restriction.    -   MAF sensor out of calibration.

While it is clear that the engine has a lack of air flow, the cause ofthis problem is still unknown. In order to isolate the cause of thisproblem it is necessary to fill the Fuel Trim load chart (FIG. 11). Thefuel trim is part of the fuel delivery feedback system. The PCM readsthe input sensor's data (MAF, RPM, IAT) and applies the data to amathematical equation, which will estimate the amount of air enteringthe engine. It will then adjust this amount by the enrichments (positiveor negative) to determine the correct injector on time. The result isfuel mapping table discussed in Paragraph [0065]. Problems such as;engine wear, dirty air filter, dirty fuel filter, will be compensatedfor by the fuel trim. A fuel trim percentage less than 10 are normalcompensations. At the point the fuel trim exceeds 10% there is a problemthat will need to be repaired. If the fuel trims loaded on the fuel trimchart are green, the fuel delivery system is working properly. If thefuel trims loaded on the fuel trim chart are yellow, orange, or red,there is a problem with the base fuel equation that is being compensatedfor by altering the injector on time. By checking the VE chart it can bedetermined whether the problem is a mechanical flow problem or anelectronic problem. If the actual VE reading is low and the fuel trimchart is green, this is an indication there is a mechanical flow problemsuch as; restricted exhaust, camshaft out of time, worn engine orcomponents. If the chart is green this would indicate that the originalfuel calculation was correct. This means all of the sensor inputs arecorrect and the injectors and fuel pressures are also good. To determinewhich problem is present tool 11 will instruct the technician to openthe throttle to 2000 RPM. The conditions are as follows:

-   -   If the idle vacuum is low and the vacuum at 2000 RPM is low then        the mechanical condition of the engine will be flagged.    -   If the idle vacuum is good and increases by 2 inches HG at 2000        RPM then the engine is assumed good.    -   If the idle vacuum is good and the vacuum stays the same or        drops at 2000 RPM then the exhaust is restricted.    -   To verify the exhaust is restricted, a cat efficiency test is        run. If the cat is melted or plugged the efficiency is very low.

If all tests pass, tool 11 will ask the technician to snap the throttle.Tool 11 now monitors the TPS and the vacuum by watching how quickly theengine gains vacuum as the throttle closes. It can be determined whetheror not the exhaust has a slight restriction. If all previous tests passthe technician will be instructed to check the cam and crank sensorsignals for proper timing correlations. If the VE is low and the fueltrim chart has large corrections indicated by yellow, orange or red, theMAF sensor is out of calibration. If the actual VE reading is normal andthe fuel trim chart loads with yellow, orange and red then this is anindication of the following:

-   -   The sensors are misreading.    -   The fuel injectors have a problem.    -   The fuel pressure is wrong.

If all sensors test good then the fuel trim charts will be analyzed. Theway in which the fuel trim loads in the chart will indicate the cluesnecessary to determine where the problem is located. An example of thiswould be if all of the trim cells filled at low RPM and low loads aregreen and as the engine load and RPM increases the trims turn to red. Atlow engine loads very little fuel delivery is needed. As the loadincreases the fuel demand will also increase. If the fuel supply systemsuch as a plugged fuel filter has a problem, the fuel system can keep upwith an engine under low load conditions but will fail with the engineunder high load conditions. This is why the trim cells are green wherethe fuel supply demand is low. As the fuel demand increases the trimcells turn red when trying to compensate for the inadequate fueldelivery.

In the present example, FIG. 11, if there is a mechanical problem suchas a restricted exhaust, camshaft out of time or engine worn out thenthe fuel trim table will be green. However, if the mass air flow sensoris misreading, the fuel trim table will be yellow, orange or reddepending on the extent of the problem. If the fuel trim starts at anegative number and moves to a positive number it is an indication thatthe mass air flow sensor is dirty and needs to be cleaned. As afollow-up, the MAF sensor was removed and cleaned and the Vol Eff testrun again. As is apparent from FIG. 12, this corrected the problem. Oncethe MAF sensor was cleaned, the Toyota was taken for a test drive. As isevident from FIG. 13, the loaded full trim chart verifies that thevehicle was correctly repaired.

FIGS. 14-17 relate to a 1999 GMC Sierra with a low power problem. FromFIG. 14 is it apparent that no DTC codes are present. However, for thevolumetric efficiency test, FIG. 15, it is clear that the VE is readinglow. The vehicle was then driven to load the fuel trim chart. The greenon the chart in FIG. 16 shows that the MAF is reading air flowcorrectly. This indicates that the engine has a restricted exhaust. Thecatalytic converter was replaced and the VE retested. The charts in FIG.17 indicate that replacement was the correct repair.

FIGS. 18 and 19 relate to a 1999 Dodge truck with a check engine lighton. The codes were pulled and, as indicated in FIG. 18 the DTC code is“catalyst system efficiency below threshold”. A catalyst efficiency testwas run, FIG. 19, which clearly shows that the converter has failed.

FIG. 20 relates to a vehicle with 2 front sensors 2 rear sensors, andboth a bad and a good catalytic converter.

FIG. 21 relates to a vehicle with a catalyst efficiency code. Thecatalyst efficiency test was run and the catalytic converters are good.The TSBs (technical service bulletins) were checked and this vehicle wasreprogrammed to fix this problem.

Simulated Injector Examples

To further the probability of finding where the problem is located atest sequence is run that is called the simulated injector. This testputs together the VE test and the fuel trim test. The power test is alsorun at this time. The results will give a better prediction on where theproblem within the fuel injection system is located. In FIG. 23 a GM 5.3liter VIN T is run. There is no problem with this engine. The fuel trimchart has been run and is loaded with all green indicating the base airequation is correct. In FIG. 24 the VE chart has been run and is loadedwith green indicating the mass air flow sensor is reading correctly andthe engine is functioning correctly. The red square is present due tothe throttle being opened very quickly. This test is being run with thethrottle set to zero. This allows the chart to load from idle to wideopen. Usually this throttle setting is at 20%. In FIG. 25 the SimulatedInjector chart is then loaded. The chart is loaded green indicatingthere is no problem present. In FIG. 26 the Power chart is then loaded.The engine produced 200 horse power indicating good power.

The next example was run on the same GM 5.3 liter VIN T. In this case,there is a leak at the intake boot between the MAF sensor and thethrottle body. In FIG. 27 the Fuel Trim charts have been loaded. Thechart shows that the vehicle's microprocessor is adding fuel from idleto wide open. In FIG. 28 the VE test has been run. The VE Tableindicates that the air volume is off by 20% at idle and moves to 11% atwide open throttle. This decrease towards wide open throttle indicatesthat an air leak is present. In FIG. 29 the Simulated Injector chart isthen loaded, which is mostly green. This indicates that the problem is asensor misreading. In this case the air volume problem caused by theleak has been corrected by the vehicle's PCM. In FIG. 30 the Power charthas also been loaded showing that the power has not been lost.

The third example is a test run on the same GM 5.3 liter VIN T. In thistest the vehicle has low fuel pressure. In FIG. 31 the Fuel Trim chartis loaded and shows the vehicle's PCM is adding over 25% from idle towide open throttle. In FIG. 32 the VE Chart and VE Table is then loaded.The VE Table shows mostly green indicating the MAF sensor and mechanicalstate of the engine are good. In FIG. 33 the Simulated Injector chartwas then loaded. The Bank 1 Fuel Injector Difference (%) table indicatesthat the actual and calculated injectors are off by as much as −51%. TheBank 2 table shows a similar problem. This indicates that the problem iswithin the fuel delivery system. This is due to the fuel pressure beinglow. The fuel delivery problem is clearly shown by the SimulatedInjector chart. In FIG. 34 the Power Chart was then loaded whichindicates that the engine made 200 horse power indicating that the powerof the vehicle was good.

The next example is from a GM 2200 engine with no problems. In FIG. 35the first chart loaded is the fuel trim, which is mostly greenindicating there is no problem with the vehicle. In FIG. 36 the VE Chartand Table are loaded. This engine uses a manifold absolute pressuresensor instead of a MAF sensor. The VE Table shows mostly greenindicating the air flow into the engine is good. In FIG. 37 theSimulated Injector chart was then filled. This chart fills with mostlygreen indicating there is no problem between the actual injection timeand calculated injection time. In FIG. 38 the Power Chart was thenloaded which indicates the engine made 80 horse power which shows thereis no power loss with this engine.

The sequencing of tests in the automated test routine is set forth inFIGS. 39 A-J. During the automated test a rationality check is alsoperformed. In this testing sequence all of the PIDS are taken intoaccount and compared against one another. One basic example of therationality check is if the engine is cold the engine coolanttemperature and the intake air temperature would need to be within 5° F.within one another. If the difference in temperature is greater than 5°F. then one of the sensors is not operating correctly.

A more complicated example is that the vehicle's engine is running roughat idle with no check engine light illuminated. The conditions are asfollows:

-   -   The engine vacuum is reading low.    -   The throttle position sensor is reading closed.    -   The mass air flow sensor, MAF, reading is low.    -   The fuel trim readings are good, +/−10%.    -   The RPM is at its target idle.

The rationality of this problem is the low vacuum at idle RPM wouldindicate the following:

-   -   That the throttle plate is open.    -   The engine has a mechanical problem.    -   There is an intake vacuum leak.    -   The EGR is stuck open.

By comparing the MAF to the engine vacuum it can be determined that thethrottle position is reading correctly and is in the closed position. Bycomparing the low vacuum and the low MAF to the feedback circuit or fueltrim it can be determined that there is no vacuum leak present. If avacuum leak were present the feedback circuit would be greater than+/−10% because the vacuum leak would be allowing air to bypass the MAFsensor. In this condition the air/fuel mixture would be lean and thefeedback circuit fuel trim would have to add fuel to keep the air/fuelmixture at 14.7 to 1. This condition would indicate that the exhaust gasrecirculation could be causing this problem. The program would then askthe technician to open the throttle to 2000 RPM. If the engine vacuumincreased to a good reading this would be an indication that themechanical condition of the engine is good. The highest probability forthis problem would be that the exhaust gas EGR was stuck in the openposition. By checking for DTCs, pending DTCs, and Mode 6 data; thisinformation could be used to increase the probability of an accurateconclusion. If there were no DTCs, no pending DTCs, but Mode 6 had afailure listed for the EGR system; this would increase the probabilityof the EGR being stuck and leaking exhaust gases into the intakemanifold.

Once the testing sequence is completed and all data have been collected,the program will evaluate the flagged data and the rationality data, andwould then project a probable solution so that the technician could thencorrect the power train control system problem(s).

To make a more accurate diagnostic conclusion an exhaust gas analyzerwould be interfaced with tool 11. The internal combustion engine breaksthe air, O2, and fuel, HC, down so they can combine with one another toform new chemical compounds. This chemical reaction powers the internalcombustion engine. In order for this chemical reaction to take place,many things must occur in the correct order. When any of these eventsfail, this reaction will change. These changes will be evident in theexhaust gas traces; CO, CO2, HC, O2, Lamda, AFR and NOX, as illustratedin FIG. 40.

The exhaust gas analyzer is a device that can sense the concentration ofcertain gas molecules that are emitted out of the internal combustionengine. The internal combustion engine draws air into the cylinder wherea hydrocarbon fuel is added. The hydrocarbon fuel is then broken down inthe cylinder and, under the right conditions, can combine with oxygen.This chemical reaction provides an expanding gas that forces the pistondown producing power at the engine's fly wheel. At the end of theburning cycle of the hydrocarbon fuel the gases are forced out of thecylinder into the exhaust system. The exhaust gas analyzer takes a smallsample of this gas as it leaves the tail pipe of the vehicle. Thissample is then pumped by the gas analyzer from the tail pipe through afiltering system into the exhaust gas analyzer's sample tube. Located atone end of the sample tube, a wide band infrared emitter is mounted.This emitter is positioned where it can send infrared light down thesample tube of the exhaust gas analyzer. At the opposite end of thesample tube an infrared quad collector is located. This collector canread the infrared light that was sent down the sample tube. Each gasthat is emitted out of the vehicle's tail pipe absorbs certain infraredlight wavelengths. If the collectors are tuned by applying lightfrequency filters only the light wavelength associated with the gas tobe sampled will pass through the filter to be read by the collector. Theamount of infrared light that passes through the sample tube and thelight filters will show the concentration of a particular gas. Theinternal combustion engine produces exhaust gas concentrations of carbonmonoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), oxygen (O2), andnitrogen oxides (NOx). These different gasses absorb different infraredlight wavelengths. The infrared light wavelength that CO absorbs is 4.65nanometers. CO2 absorbs 4.2 nanometers. HC absorbs 3.4 nanometers. NOxabsorbs 6 nanometers; however water vapors also absorb 6 nanometers oflight so NOx must be read by a chemical cell. Oxygen does not absorb anyinfrared light so it to must be read by a chemical cell. A 4th collectoris added as a gas reference and is read at 4 nanometers of infraredlight. This reference adds stability to the reading of the other gases.If no gases are in the sample tube the collectors will read the highestconcentration of infrared light. This high concentration of infraredlight shows that no gases are present in the sample tube and the gasanalyzer will display zero.

If gas traces are in the sample tube they will absorb a portion of theinfrared light. The more gas concentration, the less infrared lightmakes it to the infrared collectors. The less infrared light that ispicked up and read by the collectors, the higher the concentration ofgas content is indicated by the gas analyzer. By filling the sample tubewith a known concentration of gas content, the gas analyzer can becalibrated to a very accurate level. The exhaust gas analyzer can nowgive data that can be used by the technician or a microprocessor to helpdiagnose the internal combustion engine.

Tool 11 reads these changes and compares this data with the PIDS whichwill significantly increase the probability of a correct conclusion.Furthermore, when checking an oxygen sensor or wide range air fuelsensor, WRAF, the PIDS will provide the electrical data necessary to seeif the O2 sensor is functional but will not determine whether or not theO2 sensor or WRAF sensor is out of calibration. In order to check theoxygen sensor or WRAF sensors accuracy a gas analyzer will be used. Bycomparing the data from the PIDS and the data from the exhaust gasanalyzer, tool 11 can arrive at a conclusion on the calibration oraccuracy of the oxygen sensor or WRAF sensor.

Whereas the drawings and accompanying description have shown anddescribed the preferred embodiment of the present invention, it shouldbe apparent to those skilled in the art that various changes may be madein the form of the invention without affecting the scope thereof.

1. A method of determining with the aid of instrumentation including amicroprocessor whether an engine's rated horsepower has changed; theengine having a rated horsepower; the engine having an associatedpowertrain control module and an air induction system; the air inductionsystem including at least one sensor used to determine air flow throughthe engine; the microprocessor being programmed to extract parameteridentification data (hereinafter “PID data”), including fuel trim PIDdata, from the powertrain control module; the microprocessor also beingprogrammed with an algorithm which permits the calculation of theengine's horsepower; the method including the steps of: a. acquiring PIDdata from the powertrain control module with the instrumentation, thePID data including fuel trim PID data and PID data from the at least onesensor; b. determining the actual air flow through the engine(weight/unit of time) with PID data from the at least one sensor; c.determining the calculated horsepower of the engine with the algorithm,the actual air flow and the fuel trim PID data; and d. comparing thecalculated horsepower to the rated horsepower of the engine.
 2. Themethod as set forth in claim 1 wherein the instrumentation is providedwith a chart of engine power vs. time, further including the steps of:a. graphing the rated horsepower on the chart; b. graphing thecalculated horsepower on the chart; and c. superimposing one of thegraph of one rated horsepower and the graph of calculated horsepowerover the other of the graph of rated horsepower and the graph ofcalculated horsepower.
 3. The method as set forth in claim 1 wherein theinstrumentation is provided with a table of engine load vs. engine speed(RPM), wherein the step of comparing the calculated horsepower to therated horsepower includes determining the percentage difference betweenthe rated horsepower and the calculated horsepower at various enginespeeds and engine loads, and further including the step of assigning oneor more of the determined percentage differences to the table.
 4. Themethod as set forth in claim 3 wherein the table is divided into anumber of cells, each cell representing a separate range of engine loadsvs. engine speeds, and wherein the step of assigning includes assigningthe percentage differences to the cells which represent the enginespeeds and engine loads at which the differences were determined.
 5. Themethod as set forth in claim 4, further including the steps of dividingpossible percentage differences into a series of ranges and assigningeach range a separate, distinct code.
 6. The method as set forth inclaim 5, wherein the step of assigning codes includes the step ofassigning different colors to the different ranges.
 7. The method as setforth in claim 5, further including the step of providing a first codefor percentage differences between rated horsepower and calculatedhorsepower in the range of −A and +A.
 8. The method as set forth inclaim 7, further including the step of providing a second code forpercentage differences between rated horsepower and calculatedhorsepower in the ranges of −A and −B and between +A and +B, wherein theabsolute value of B is greater than the absolute value of A.
 9. Themethod as set forth in claim 8, further including the step of providinga third code for percentage differences between rated horsepowercalculated horsepower in the ranges of −B and −C and between +B and +C,wherein the absolute value of C is greater than the absolute value of B.10. The method as set forth in claim 9, further including the step ofproviding a fourth code for percentage differences greater than +C andless than −C.
 11. The method as set forth in claim 10 wherein theinstrumentation includes a visual monitor, wherein the table isdisplayed on the monitor, wherein the first code is assigned a firstcolor, the second code is assigned a second color, the third code isassigned a third color, and the fourth code is assigned a fourth color.12. The method as set forth in claim 11, further including assigninggreen as the first color and assigning red as the fourth color.
 13. Themethod as set forth in claim 11, further including the steps ofassigning a value of 10 to A, a value of 13 to B and a value of 16 to C.14. An automotive diagnostic table embodied on instrumentation includinga microprocessor for use in association with a method of determining thepercentage difference between the rated horsepower of an engine and thehorsepower calculated at various engine loads and engine speeds, thetable including a first axis representing increasing values of engineload and a second axis representing increasing engine speed, the tablefurther including a plurality of cells, each cell representing adifferent range of engine loads vs. engine speeds, at least some of thecells representing the percentage difference between the calculatedhorsepower of an engine and the rated horsepower of such engine.
 15. Amethod of calculating the horsepower of an engine with the aid ofinstrumentation including a microprocessor; the engine having anassociated powertrain control module and an air induction system; theair induction system including at least one sensor used to determine airflow through the engine; the microprocessor being programmed to extractparameter identification data (hereinafter “PID data”) data, from thepowertrain control module; the microprocessor also being programmed withan algorithm which permits the calculation of the engine's horsepower;the method including the steps of: a. acquiring PID data from thepowertrain control module with the instrumentation, including PID datafrom the at least one sensor; b. determining the actual air flow throughthe engine (weight/unit of time) with PID data from the at least onesensor; and c. determining the calculated horsepower of the engine withthe algorithm.
 16. The method as set forth in claim 15 wherein the stepof acquiring PID data includes acquiring fuel trim PID data, and whereinthe step of determining the calculated horsepower includes determiningwith the algorithm, the actual air flow and the fuel trim PID data.